1. Field of the Invention
The present invention relates generally to a prosthetic foot with a variable stiffness sole plate.
2. Related Art
Many individuals have lost a limb for various reasons including war, accident, or disease. In most instances these individuals are not only able to live relatively normal lives, but physically active lives as well. Oftentimes, these individuals are aided in their everyday lives by a prosthetic limb. The objective of prosthesis is to provide an artificial limb that simulates the function and natural feel of the replaced limb.
With respect to prosthetic feet, the development of a functional and natural artificial foot has been limited by material and imagination. Many designs have attempted to copy the anatomy of the foot or simulate its actions by replacing the bones and muscle with various mechanical simulation by replacing the entire foot with an energy storage element such as a spring. As the user steps onto the foot, the user's weight compresses the spring. As the user moves forward, the user's weight comes off the foot and the energy stored in the spring is used to propel the user forward.
Almost all of the past designs have focused on the major aspect of the prosthetic foot movement of the ankle or foot as it relates to walking or running. Few designs consider the lateral, or side to side rotation of the foot when the foot is used on varied or uneven terrain. It will be appreciated that the forefoot of a natural foot rotates with a medial to lateral roll-over to accommodate variations in terrain. Most artificial feet of previous designs usually incorporate a unitary foot that is incapable of such movement.
Some designs have attempted to mimic the lateral rotation of the natural by splitting the forefoot region of the artificial foot longitudinally from the toe toward the heel, thereby effectively creating one or more “toes” on the prosthetic foot. This design is problematic, however, because the split creates at least two forefoot regions that can bend independent from one another and can result in an unnatural, out of balance feel to the user.